Progress in intense ion beam research for inertial confinement fusion at Cornell University

Recent studies of time integrated and time dependent ion beam divergence using two magnetically insulated diodes at 10¹⁰–10¹¹ W show a directionality which is apparently a result of electron dynamics and/or anode plasma nonuniformities in the diodes. Beam uniformity, divergence, and “aiming error” are dependent upon the detailed diode structure and operating conditions. Experiments performed on the 10¹² W LION acceleration show a ≲40% energy coupling from the magnetically insulated transmission line to an annular magnetically insulated diode, with >10⁹ W/cm² beams at up to 1.5 MeV being generated. This diode utilizes an applied radial magnetic field and the self-field of the ion current to provide the total magnetic field needed to cut off the electron flow across the accelerating gap. Computer simulations of the propagation of 3–7 MeV, 1–2 MA proton beams in a 0.6 cm radius plasma channel have been performed using a 2-1/2 D hybrid CIDER code. Results suggest that 75% of the beam energy can be transported in a 4 m long channel.